Image sensor

Abstract

An image sensor according to the present invention includes a charge forming portion forming charges by photoelectric conversion and a charge transfer region including a charge increasing region for increasing the amount of charges. The image sensor is so formed as to increase dark current generated in at least part of the charge forming portion and the charge transfer region in the charge increasing region for calculating an increasing ratio for the charges on the basis of an output value resulting from a charge signal of the increased dark current.

1 . An image sensor comprising:
 a charge forming portion forming charges by photoelectric conversion; and   a charge transfer region including a charge increasing region for increasing the amount of charges,   for increasing dark current generated in at least part of said charge forming portion and said charge transfer region in said charge increasing region and calculating an increasing ratio for said charges on the basis of an output value resulting from a charge signal of increased said dark current.   
     
     
         2 . The image sensor according to  claim 1 , so formed as to increase said dark current with at least three types of frequencies for calculating said increasing ratio for said charges on the basis of respective output values resulting from said charge signal of said increased dark current. 
     
     
         3 . The image sensor according to  claim 2 , increasing said dark current with three types of frequencies including a first frequency with which an output value resulting from said charge signal of said increased dark current is larger than a minimum detectable value, a second frequency, larger than said first frequency, with which an output value resulting from said charge signal of said increased dark current is smaller than a maximum detectable value and a third frequency substantially corresponding to the average of said first frequency and said second frequency. 
     
     
         4 . The image sensor according to  claim 2 , so formed as to calculate said increasing ratio for said charges as an increasing ratio per increasing frequency for said dark current. 
     
     
         5 . The image sensor according to  claim 4 , so formed as to acquire an increasing ratio for said charges with an arbitrary increasing frequency on the basis of calculated said increasing ratio per increasing frequency for said dark current. 
     
     
         6 . The image sensor according to  claim 2 , so formed as to acquire said increasing ratio for said charges by increasing said dark current with at least three types of frequencies, calculating at least three increasing ratios on the basis of respective output values resulting from said charge signal of said increased dark current and thereafter averaging said three increasing ratios. 
     
     
         7 . The image sensor according to  claim 1 , increasing both of dark current generated in said charge forming portion and dark current generated in said charge transfer region. 
     
     
         8 . The image sensor according to  claim 1 , further comprising:
 an effective pixel region, and   an optical black pixel region provided to surround said effective pixel region, wherein   each of a pixel of said effective pixel region and a pixel of said optical black pixel region includes said charge forming portion, a voltage conversion portion and said charge transfer region having said charge increasing region,   for increasing dark current generated in at least part of said charge forming portion and said charge transfer region provided on said pixel of at least either said optical black pixel region or said effective pixel region.   
     
     
         9 . The image sensor according to  claim 8 , increasing dark current generated in at least part of said charge forming portion and said charge transfer region provided on said pixel of at least said optical black pixel region in said optical black pixel region and said effective pixel region. 
     
     
         10 . The image sensor according to  claim 9 , increasing dark current generated in at least part of said charge forming portion and said charge transfer region provided not on said pixel of said effective pixel region but on said pixel of said optical black pixel region. 
     
     
         11 . The image sensor according to  claim 8 , increasing dark current generated in at least part of said charge forming portions and said charge transfer regions provided on said pixels of both of said optical black pixel region and said effective pixel region. 
     
     
         12 . The image sensor according to  claim 8 , increasing dark current generated in at least part of said charge forming portion and said charge transfer region provided on said pixel of at least said effective pixel region in said optical black pixel region and said effective pixel region while increasing said dark current in a state shielding said effective pixel region from light. 
     
     
         13 . The image sensor according to  claim 8 , increasing said dark current with different frequencies in said optical black pixel region and said effective pixel region. 
     
     
         14 . The image sensor according to  claim 8 , increasing dark current generated in one prescribed pixel of at least either said optical black pixel region or said effective pixel region. 
     
     
         15 . The image sensor according to  claim 1 , wherein
 said charge increasing region is so formed as to increase the amount of charges of said dark current by impact ionization.   
     
     
         16 . A CMOS image sensor comprising:
 a charge forming portion forming charges by photoelectric conversion; and   a charge transfer region including a charge increasing region for increasing the amount of charges, wherein   said charge increasing region is provided every pixel,   for increasing dark current generated in at least part of said charge forming portion and said charge transfer region in said charge increasing region and calculating an increasing ratio for said charges on the basis of an output value resulting from a charge signal of increased said dark current.   
     
     
         17 . The CMOS image sensor according to  claim 16 , so formed as to increase said dark current with at least three types of frequencies for calculating said increasing ratio for said charges on the basis of respective output values resulting from said charge signal of said increased dark current. 
     
     
         18 . The CMOS image sensor according to  claim 17 , increasing said dark current with three types of frequencies including a first frequency with which an output value resulting from said charge signal of said increased dark current is larger than a minimum detectable value, a second frequency, larger than said first frequency, with which an output value resulting from said charge signal of said increased dark current is smaller than a maximum detectable value and a third frequency substantially corresponding to the average of said first frequency and said second frequency. 
     
     
         19 . The CMOS image sensor according to  claim 16 , increasing both of dark current generated in said charge forming portion and dark current generated in said charge transfer region. 
     
     
         20 . The CMOS image sensor according to  claim 16 , further comprising:
 an effective pixel region, and   an optical black pixel region provided to surround said effective pixel region, wherein   each of a pixel of said effective pixel region and a pixel of said optical black pixel region includes said charge forming portion, a voltage conversion portion and said charge transfer region having said charge increasing region,   for increasing dark current generated in at least part of said charge forming portion and said charge transfer region provided on said pixel of at least either said optical black pixel region or said effective pixel region.